MUC2 expression is regulated by histone H3 modification and DNA methylation in pancreatic cancer

Abstract

Mucins are highly glycosylated proteins that play important roles in carcinogenesis. In pancreatic neoplasia, MUC2 mucin has been demonstrated as a tumor suppressor and we have reported that MUC2 is a favorable prognostic factor. Regulation of MUC2 gene expression is known to be controlled by DNA methylation, but the role of histone modification for MUC2 gene expression has yet to be clarified. Herein, we provide the first report that the histone H3 modification of the MUC2 promoter region regulates MUC2 gene expression. To investigate the histone modification and DNA methylation of the promoter region of the MUC2 gene, we treated 2 human pancreatic cancer cell lines, PANC1 (MUC2-negative) and BxPC3 (MUC2-positive) with the DNA methyltransferase inhibitor 5-azacytidine (5-aza), the histone deacetylase inhibitor trichostatin A (TSA), and a combination of these agents. The DNA methylation level of PANC1 cells was decreased by all 3 treatments, whereas histone H3-K4/K9 methylation and H3-K9/K27 acetylation in PANC1 cells was changed to the level in BxPC3 cells by treatment with TSA alone and with the 5-aza/TSA combination. The expression level of MUC2 mRNA in PANC1 cells exhibited a definite increase when treated with TSA and 5-aza/TSA, whereas 5-aza alone induced only a slight increase. Our results suggest that histone H3 modification in the 5 0 flanking region play an important role in MUC2 gene expression, possibly affecting DNA methylation. An understanding of these intimately correlated epigenetic changes may be of importance for predicting the outcome of patients with pancreatic neoplasms. ' 2006 Wiley-Liss, Inc.

Coordinate Regulation of the Gel-forming Mucin Genes at Chromosome 11p15.5*

“…It is likely based on data from other loci (29,53,54) that CTCF suppresses gene expression by recruiting a repressive complex such as the polycomb group repressor complex 2 or SIN3A and associated histone deacetylases. Consistent with these observations, previous reports showed an increase in MUC2 expression following histone deacetylase 2 depletion (19) and that expression of MUC2 was apparently dependent on H3K9 and H3K27 acetylation in the 5Ј-flanking region (55). However, our data showing that CTCF depletion increases expression of MUC2, MUC5AC, and MUC6 in different cell lines are in contrast with observations that only MUC2 and MUC5B are subject to epigenetic regulation, with MUC5AC being rarely influenced and MUC6 not at all (19).…”

Regulation of Airway Mucin Gene Expression

“…Several notable CpG sites in the wider area of the MUC2 promoter region, including those in AP2 and Sp1 binding motifs, showed obvious differences in methylation level between PANC1, BxPC3, and normal colonic crypt cells (145). Similar observations showing that site-specific methylation can downregulate MUC2 gene expression have been reported in pancreatic cancer cells (142,146). These specific sites of methylation changes in the promoters may be a road map to the critically important regulatory regions of MUC2.…”

“…One study examined the histone deacetylase inhibitor trichostatin A (TSA) on MUC2 expression in pancreatic cancer cell lines. Treatment with TSA resulted in the upregulation of MUC2 expression, suggesting that histone acetylation can to some degree turn on the MUC2 gene (146). In the future, further studies in other epigenetic mechanisms, including histone modification and chromatin modification in MUC2 inactivation, are expected.…”

Expression of MUC2, MUC5AC, MUC5B, and MUC6 mucins in colorectal cancers and their association with the CpG island methylator phenotype

“…Several studies have examined the expression of various mucin genes in relation to the nature and extent of CpG island methylation, and have found that MUC2 and MUC5B in particular, show strong correlations between promoter methylation and suppression of mucin protein synthesis. 23,[54][55][56][57] There is currently little or no evidence of methylation-induced silencing of either MUC5AC or MUC6. 23 Furthermore, MUC17, a transmembrane mucin gene, is regulated by promoter CpG island methylation and histone H3-K9 acetylation in pancreatic ductal adenocarcinomas, where promoter hypomethylation is associated with MUC17 expression.…”